This invention relates to ultraviolet light absorbing polymer compositions and more particularly, to polymer compositions including polyurethane elastomers and covalently bonded ultraviolet light absorbing components. The subject polymer compositions, which are preferably optically clear, may be used in the fabrication of ultraviolet light absorbing ocular devices such as corneal contact lenses, intraocular lenses, and corneal intrastromal implant lenses.
The incident light entering the eye is composed of the entire spectrum of wavelengths including the ultraviolet, visible, and infrared. The cornea preferentially filters ultraviolet light up to about 300 nm. The natural lens normally screens ultraviolet light in the range of about 300 nm to about 400 nm. Thus, in the eye with its natural lens in place relatively little radiation of wavelengths less than about 400 nm reaches the posterior intraocular structures, e.g., the vitreous humor and the retina.
In the aphakic individual, i.e., that individual who has had the natural crystalline lens removed, there is a loss in protection for the retina from ultraviolet light in the above-noted range. Thus, the use of ultraviolet light absorbing contact or intraocular lenses is particularly important for the aphakic person. It is further believed that ultraviolet light screening spectacles or contact lenses may retard the development of a cataract in the natural lens.
Although low molecular weight, non-polymerizable ultraviolet absorbing compounds of various types are effective in blocking ultraviolet radiation when compounded into polymer formulations, their extractability in various media may limit their utility. This problem is remedied by the synthesis of polymerizable, ultraviolet-absorbing monomers which can be covalently coupled into the polymer matrix. These covalently bonded ultraviolet light absorbing monomers are not extractable. Articles fabricated from ultraviolet light absorbing polymer compositions incorporating these polymerizable ultraviolet light absorbing monomers therefore maintain stable ultraviolet screening characteristics.
It is known that certain polymerizable derivatives of 2-(2-hydroxyphenyl)-2H-benzotriazole are efficient ultraviolet light absorbing species that can be copolymerized into a variety of polymeric materials. Commonly assigned, co-pending application Ser. No. 109,727, filed Oct. 16, 1987, discloses ultraviolet light absorbing compositions derived from vinyl functional monomers and certain vinyl functional, ultraviolet light absorbing derivatives of 2-(2-hydroxyphenyl)-2H-benzotriazole. Commonly assigned, co-pending application Ser. No. 122,945, filed Nov. 19, 1987), discloses silicone elastomers which include covalently bonded UV light absorbing components. Each of these latter two applications is incorporated in its entirety by reference herein.
In J. Macromol Sci.-Chem. A 22(4), p. 382-402 (1985), Dickstein and Vogl disclose 2-(2-hydroxy-5-vinylphenyl)-2H-benzotriazole being co- and terpolymerized with N-vinylpyrrolidone and various methacrylic esters. The polymerizations result in polymers from which the ultraviolet light absorbing component cannot be extracted or leached out. The polymers have water absorption behavior similar to that of co- and terpolymers without the incorporation of the ultraviolet light absorbing component.
Beard, et al, U.S. Pat. No. 4,528,311, discloses ultraviolet light absorbing polymer compositions comprising copolymers of 2-(2hydroxy-5-acrylyloxyphenyl)-2H-benzotriazoles with one or more other vinyl monomers, specifically acrylic monomers such as methyl methacrylate. This patent also discloses that such benzotriazole compounds may be used as additives to a wide variety of organic polymers, including polyurethanes and polyureas, to impart ultraviolet light absorbing properties to the polymer, which is useful in the manufacture of ocular devices. In example 4, the preparation of the intermediate 2-(2-hydroxy-5-hydroxypropyl-3-t-butylphenyl)-5-chloro-2H-benzotriozole is disclosed. There is no indication, however, of a benzotriazole-type compound having a single reactable hydroxyl group which is functional in a polymerization reaction with polyurethanes or polyurethane-ureas.
Besecke, et al U.S. Pat. No. 4,612,358 discloses the use of certain benzotriazole derivatives, in particular 2-(2-hydroxy-3-methacrylamidomethyl-5-t-octyphenyl) benzotriazole, having ultraviolet light absorbing properties in polymers with unsaturated vinyl or vinylidene monomers. Besecke et al does not disclose benzotriazole-type compounds having a hydroxyl group which is functional in a polymerization reaction.
Szycher U.S. Pat. Nos. 4,131,604 and 4,285,073 disclose polyurethane compositions useful as bladders for heart pumps, and as artificial cornea and permanently implantable lenses, respectively. Neither patent discloses any benzotriazole compound nor any ultraviolet light absorbing component.
Other U.S. Patents which were considered in preparing this application are U.S. Pat. Nos. 4,304,895, 4,390,676, 4,636,212 and 4,158,030.
Materials used to manufacture ocular devices, such as contact lenses, intraocular lenses and corneal intrastromal implant lenses should be capable of absorbing ultraviolet light for the aphakic patient. The ultraviolet light absorber should be capable of absorbing radiation in the range of about 300 nm to about 400 nm.